Twinblade Assassins — ruling 1

If a creature didn't die before your end step begins, the ability of Twinblade Assassins doesn't trigger at all. The creature may have died before Twinblade Assassins entered the battlefield, however.

Twinblade Assassins — ruling 2

The triggered ability triggers just once, no matter how many creatures died this turn.

Twinblade Assassins : règles, fonctionnement et interactions (MTG)

Twinblade Assassins is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

At the beginning of your end step, if a creature died this turn, draw a card.

How it works : Twinblade Assassins

Original English text — Wizards of the Coast / Scryfall

#1June 23, 2020· Wizards of the Coast
If a creature didn't die before your end step begins, the ability of Twinblade Assassins doesn't trigger at all. The creature may have died before Twinblade Assassins entered the battlefield, however.
No other card is named in this ruling.
#2June 23, 2020· Wizards of the Coast
The triggered ability triggers just once, no matter how many creatures died this turn.
No other card is named in this ruling.